Writing instrument and welding method of writing point assembly and writing instrument parts connecting structure and connecting method

ABSTRACT

The object is to provide a writing instrument and a welding method of a writing point assembly as well as writing instrument parts connecting structure and connecting method, wherein the writing point assembly and an ink tube or/and a holder can be welded appropriately at a necessary area only without using ultrasonic waves, so as to be able to prevent dislodging of the writing point assembly, ink leakage and the like. The rear end part, of a metallic writing point assembly as a part of a writing instrument, which is inserted into a joint, is heated at the predetermined area (at least the fitted area in contact with the front end part of the joint), so as to weld the predetermined area of the writing point assembly to the surrounding part of the joint.

TECHNICAL FIELD

The present invention is directed to welding of a writing point assemblyfor a writing instrument, and in particular relates to a writinginstrument and a welding method for a writing point assembly as well asa writing instrument parts connecting structure and connecting method,for prevention against gas leakage of a pressurized ball-point pen andbreakage of a writing point assembly from press-fitting.

BACKGROUND ART

There are various types of writing instruments such as fountain pens,mechanical pencils and others. Ball-point pens are one of these. Of theball-point pens, pressurized ball-point pens which are filled up withpressurized gas are known, which have a structure, as disclosed in U.S.Pat. No. 4,472,462 or U.S. Pat. No. 3,997,273, including a joint as aholder for joining the rear end of a writing point assembly as a writingpart and the open front part of an ink tube and an inner barrel fittedto the joint by bonding, tight fitting or other methods, wherein theinner barrel is filled up with a pressurized gas such as air, nitrogengas or the like.

In such pressurized ball-point pens, mere press fitting of the pointassembly into the joint or ink tube poses the risk of dislodging thewriting assembly due to sealed gas pressure, ambient temperatureinfluences or creep with passage of time. There is also a gas leakageproblem occurring due to micro damages during assembly or other reasons.Similarly, even in the case of ordinary writing instruments other thanthe pressurized ball-point pens, there are cases where the resin jointor ink tube may crack when the point assembly with a writing part ispress fitted so that ink will not leak out.

In order to solve these problems, conventionally a flexible resin thatis inferior in the other characteristics, has been used, or a method offorming an annular groove in the writing point assembly at the part tobe inserted into the ink tube has been adopted. Alternatively, a specialshape may be formed so that molten resin by the effect of ultrasonicwaves is flowed into annular grooves etc. Also, the holder may be weldedby ultrasonic heating to the front end of the barrel to which thewriting point assembly is fitted, so that the writing point assembly isfixed by a joint that that externally fits on the writing pointassembly.

However, when ultrasonic waves are used for welding, the writing pointassembly is affected by ultrasonic waves, possibly causing damage to thewriting part and inducing problems such as dislodging of the ball fromthe tip of the writing point assembly, ink blotting or ink flushing, orsplitting during writing. Further, it is impossible to maintain theinitial strength of the writing point assembly at the part that isinserted into the ink tube, due to external force, influence fromambient temperature, creep deformation and cracks and others of thematerial itself. As a result, there occur problems such as dislodging ofthe writing point assembly, ink leakage, self-heating of the entirewriting instrument, instability of welding and the like.

Further, in the conventional writing instruments, since the inner barrelis merely fitted to the joint, there is a risk of the pressurized gasleaking out if the joint is not fixed fast to the inner barrel. Thisalso becomes a cause that may induce ink leakage and other problems.

In order to solve these problems, forcible press fitting or sealantapplication may be done for a case of metal. For a case of resin, thejoint and the inner barrel may be joined by firm fitting usingultrasonic waves or the like. These methods however need difficultassembly or high cost, and also entails the risk of dislodging of theball held by the writing point assembly, ink blotting and flushing andother new critical problems occurring.

DISCLOSURE OF INVENTION

The present invention has been devised in view of the above, and it isan object of the present invention to provide a writing instrument and awelding method of a writing point assembly, wherein the writing pointassembly and an ink tube or/and a holder can be welded appropriately atonly a necessary area without using ultrasonic waves, so as to be ableto prevent dislodging of the writing point assembly, ink leakage and thelike. It is another object to provide a writing instrument partsconnecting structure and connecting method, capable of joining thewriting instrument parts, for example, a joint and an inner barrel,firmly to prevent leakage of fluids such as gas, ink and the like.

According to the present invention defined in claim 1, in order toachieve the above objects, a writing instrument comprises: a writingpoint assembly having a writing part at the front end thereof; and anink tube for storing ink therein, and is characterized in that thewriting point assembly is formed of metal, and the writing pointassembly is welded to a holder or/and the ink tube around the writingpoint assembly by heating the writing point assembly at a predeterminedarea that is fitted into the holder or/and the ink tube so that theresin around the predetermined area of the writing point assembly fusesor softens to create tight contact.

Herein, the heated portion of the writing point assembly may be formedof stainless steel.

Also, a pressurized gas may be sealed in the interior forming apressurized ball-point pen.

The holder may be formed of a resin presenting a tensile elongation of20% or less (based on ASTMD638) such as polycarbonate, ABS, cyclicpolyolefin, modified polyphenylene ether, polystyrene or the like, andthe holder and the writing point assembly may be welded.

The present invention defined in claim 5 is a welding method of thatdefined in any one of claims 1 to 4, and is characterized in that onlythe rear end part of the writing point assembly is heated withoutheating the front end part of the writing point assembly.

The present invention defined in claim 6 is a welding method of thatdefined in any one of claims 1 to 4, and is characterized in that thepredetermined area of the writing point assembly made of metal isinduction heated with an electromagnetic induction coil.

The present invention defined in claim 7 is a welding method of thatdefined in any one of claims 1 to 4, and is characterized in that therear end of the writing point assembly is welded by heating with aheated trowel.

Herein, for heating induction heating using an electromagnetic coil maybe chosen.

Also, the rear end part of the writing point assembly is welded byheating with a heated trowel.

The present invention defined in claim 10 is a writing instrument partsconnecting structure for connecting parts of a writing instrument, andis characterized in that each part is formed of resin, a conductor isarranged between the parts, and each part is welded to the conductor.

The present invention defined in claim 11 is a writing instrument partsconnecting structure for connecting a joint and a cylindrical element aswriting instrument parts, and is characterized in that the joint andcylindrical element are separately formed of resin, a conductor isprovided between the joint and the cylindrical element, and theconductor, joint and cylindrical element are welded.

Herein, the joint may be interposed between the point assembly and theink tube of the writing instrument so as to join these elements and thecylindrical element may be made to serve as an inner barrel of thewriting instrument so as to cover the ink tube.

It is preferred that the conductor is in the form of a stainless steelring.

It is also preferred that the conductor may be heated and welded usingelectromagnetic induction heating.

Further, the present invention defined in claim 15 is a writinginstrument parts connecting method for connecting parts of a writinginstrument, comprising the steps of: forming each part from resin;arranging a conductor between the parts; and heating the conductor byelectromagnetic induction to weld each part to the conductor.

Moreover, the present invention defined in claim 16 is a writinginstrument parts connecting method for a joint and a cylindricalelement, both made of resin, comprising the steps of: arranging anannular conductor between the joint and the cylindrical element; andheating the conductor by electromagnetic induction to weld the joint andthe cylindrical element.

It is preferred that the conductor is given in the form of a stainlesssteel ring.

Herein, the parts of a writing instrument at least include a joint and acylinder element. Other than these, a tail plug and a cylindricalelement, a point assembly and a joint, and a point assembly and an inktube are included for example. However, these are mere examples and theparts are not particularly limited. The parts of the writing instrumentmay be transparent, translucent or opaque. As the conductor, those in aring form are used mainly. However, a barrel-like cylinder may be used.A plurality of magnetic pieces may be applied to the outer peripheralsurface of the joint. Application of a magnetic paint, a spring,plating, etc. may be made use of. Further, the parts connectingstructure and connecting method are mainly used for writing instruments,however, they can also be applied appropriately to a relativelyinexpensive articles that demand similar leakage resistance or aestheticappearance, such as cosmetic products that handle various liquids andgases.

According to the present invention, as the parts such as a joint and acylindrical element are heated so as to be welded (fused to join), astrong connecting force can be obtained, whereby it is possible toeffectively prevent leakage of pressurized gas and leakage of ink.

Further, when a conductor as an object to be heated is induction heatedby application of an electromagnetic field, electric energy istransferred to (electric current is induced within) the conductor, theconductor itself converts the electric current into Joule heat. Withthis conversion to Joule heat, in other words, eddy current loss, thejoint and the cylindrical element, both made of resin, become welded attheir opposing faces.

When stainless steel is used for the conductor, thermal generationimproves from the magnitude of the current resistance to eddy currentimproves and rust resistance and thermal degradation improve as well.Further, when the conductor is given in a ring form, weldability andeddy current efficiency also improve.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a partial illustrative view showing a pressurized writinginstrument in the first embodiment of a writing instrument and a weldingmethod of a writing point assembly according to the present invention.

FIG. 2 is an illustrative view showing a state where the writing pointassembly in the first embodiment is fitted to a joint and weldedthereto.

FIG. 3 is a partial illustrative view showing a gel ball-point pen inthe second embodiment of the present invention.

FIG. 4 is a sectional illustrative view showing an embodiment of awriting instrument parts connecting structure according to the presentinvention.

FIG. 5 is a sectional illustrative view showing a joint and a writingpoint assembly in the embodiment of a writing instrument partsconnecting structure according to the present invention.

FIG. 6 is a plan view showing a conductive ring in the embodiment of awriting instrument parts connecting structure according to the presentinvention.

FIG. 7 is a sectional view of FIG. 6.

BEST MODE FOR CARRYING OUT THE INVENTION

A preferred embodiment of a writing instrument and a method of welding awriting point assembly according to the present invention willhereinbelow described with reference to the drawings. FIG. 1 is anillustrative vertical sectional view partially showing the front end ofa pressurized ball-point pen refill according to the first embodiment ofa writing instrument and a welding method of a writing point assembly.FIG. 2 is an illustrative view showing a state of the writing pointassembly and a joint being fitted and fixed in FIG. 1. FIG. 3 is anillustrative vertical sectional view showing the front end part of a gelink ball-point pen. Here, illustration of the barrel cylinder coveringthe refill is omitted.

In the writing instrument in the first embodiment of the presentinvention, as shown in FIG. 1, a rear end part 10, of a writing pointassembly 6 formed of metal and externally covered by a joint 1 as aholder made of resin, is inserted into the opening at the front end partof a resin ink tube 11.

Fitted externally on outer peripheral surface of joint 1 is an innerbarrel 20 that is closed at the rear end thereof. A point assemblyholder (so-called plastic mouthpiece) 4 for protecting writing pointassembly 6 is fitted from the front end part of the inner barrel 20 tothe mid part 9 of writing point assembly 6. Writing point assembly 6supports a ball 8 at a front end part 7 as a writing part in a rotatablemanner. The outer peripheral part of mid part 9 is formed to be greaterin diameter than the front end part 7 and rear end part 10. Ink tube 11is a hollow cylinder and stores ink 12 therein. This ink tube 11 isfirmly fixed to writing point assembly 6 or/and joint 1, by fitting,bonding, welding or other methods, so that ink 12 will not come out.

Joint 1 is formed in a slightly tapered, approximately cylindricalstructure, and a step is formed inside the bore at the central portion,forming a small-bore portion, narrower than the rear portion.Specifically, inserted into a large-bore portion 2, from the centralportion to the rear along the axis of the joint 1, having a greaterinside diameter is the open front end of ink tube 11. The front end part3 with its inner periphery stepped to be narrower externally fits onpart of rear end part 10 of writing point assembly 6. This front endpart 3 is stepped to be large in diameter at the frontmost end, so as toallow the stepped portion at the rear of the mid portion 9 of writingpoint assembly 6 to be inserted therein.

As shown in FIG. 1, an annular flange 5 is formed on the outer peripheryat a position closer to the front of large-bore portion 2 of joint 1, sothat inner barrel 20 that externally fits on joint 1 is fitted andpositioned until it abuts this flange 5. Further, an annular positioningflange 22 is formed on the external periphery of inner barrel 20.

Point assembly holder 4 has an overall shape that forms an approximatelyconical side. The inner periphery at its front end abuts the outerperipheral surface of mid portion 9 of writing point assembly 6 so as toprovide an anti-falling function while the rear end abuts positioningflange 22 of inner barrel 20 and the inner periphery fits the outerperiphery of inner barrel 20 (at the fitting portion indicated by a codeE). Thus, the holder can be fixed by fitting of the outer periphery ofjoint 1 and the inner periphery of inner barrel 20.

The aforementioned writing point assembly 6 is connected to ink tube 11via joint 1 while pressurized gas 21 is tightly sealed inside innerbarrel 20, thus forming a pressurized writing instrument.

Concerning the material for each of the aforementioned components, inconsideration of gas barrier performance, polypropylene or polyethylenecan be used for ink tube 11 and ethylene-vinyl copolymer (EVOH), PET,nylon, PBT, POM, polyacrylonitrile, PEN, etc. can be used for joint 1and inner barrel 20.

In this arrangement, the rear end part 10 inserted into joint 1 ofwriting point assembly 6 is heated at the predetermined area (at leastthe fitted area in contact with the front end part 3 of joint 1) 30, soas to fuse the resin at the predetermined area 30 and thereabout,thereby welding the predetermined area 30 of writing point assembly 6and the surrounding joint 1. In this case, since the front end part 7 ofwriting point assembly 6 is not heated but only the rear end part 10 isheated, it is possible to prevent adverse effects such as discoloration,deformation, degradation, etc. due to heating of unnecessary part.

The heating is preferably done by electromagnetic induction heating atthe predetermined area 30 of writing point assembly 6. This is becauseuse of induction heating makes possible heating of the target area onlywithout causing any defect such as dislodging of the ball, degradationof ink 12, flushing, welding failure, unnecessary heating of the wholepart, etc. which would occur from vibrations when ultrasonic heating isused. Further, as shown in FIG. 2, an induction coil 31 is disposed soas to be spaced from and directed to the predetermined area 30 ofwriting point assembly 6. Application of electric current through thisinduction coil 31 generates induction current in the predetermined area30 of writing point assembly 6 so that only the predetermined area 30can be heated.

The present invention, however, should not be limited to this. The rearend of writing point assembly 6 may be heated with a heated trowel. Thewriting point assembly 6 may be formed of any of various kinds of metalsas long as the metal can be heated by induction heating. In particular,stainless steel is preferred which contains ferromagnetic componentssuch as Fe (iron), Cr (chromium) etc. in greater amounts and will notrust or be oxidized by heating. Other material can be used for otherthan the heated portion if at least the predetermined area 30 or theportion to be heated is formed of stainless steel. In this case, therange of material selection can be widened so that cost reduction can beexpected.

The above writing instrument is effective when applied to a pressurizedball-point pen in which the inner barrel 20 is formed to be a hermeticspace and pressurized gas 21 such as pressurized air, nitrogen gas orthe like is charged within the interior space. This is because the abovewelding method enables the predetermined area 30 to form an air-tighthermetic structure simply and reliably. In addition, the welding isactually effective in preventing gas leakage due to vertical scratchesformed during assembly.

In the above embodiment, writing point assembly 6 is welded to joint 1,but writing point assembly 6 may be welded to ink tube 11, solo or incombination with the above welding. This produces tight and reliableadhesion between writing point assembly 6 and ink tube 11, henceproducing preferable result in view of leakage of ink 12.

Next, FIG. 3 is a partial illustrative view showing a gel ink ball-pointpen in the second embodiment of the present invention.

The differences from the first embodiment are that the writinginstrument is of a non-pressurized type and that joint 1 is formed of amaterial such as ABS, modified polyphenylene ether (modified PPE),cyclic polyolefin, polycarbonate (PC), polystyrene (PS) or the like,which is prone to crack by press fitting and which is a resin having atensile elongation of 20% or less based on ASTMD638 and being easy tocrack because of lower stretchability. Even with such resin, generationof cracks and falling of the point assembly can be prevented byheat-welding.

With the heat welding of the present invention, even polystyrene, whichis vitreous and prone to crack, can be used to achieve ink 12 or gasleakage free welding if the press fit margin is set to be very small oralmost none or even if there is a gap without any press fit margin.

Also, though there are differences in the shapes of ink tube 11 and thepoint assembly press fit portion of joint 1, the present invention isapplicable in the same manner. Further, the present invention can beapplicable in the same manner to various types of writing tips such asthose for fountain pens, maker pens, pipe pens, etc.

Next, a preferred embodiment of writing instrument parts connectingstructure and connecting method according to the present invention willbe described. In the writing instrument of this embodiment, as shown inFIGS. 4 to 7, a joint 1 and an inner barrel 20 given in a cylindricalform, both constituting a pressurized ball-point pen, are separatelyformed of resin. A conductive ring 40 which opposes, and comes intocontact with, the inner peripheral surface of inner barrel 20 is fittedon the outer peripheral surface at the terminal end of joint 1. Thisconductive ring 40 is heated by induction (called electromagneticinduction heating (IH: induction heating)) so as to weld joint 1 andinner barrel 20 in an appropriate manner.

Joint 1 is formed by injection molding using a predetermined resin,specifically, ABS, PP, PS, PE, recycled plastics, etc., which isexcellent in impact resistance, mechanical properties and the like, or amaterial also considering gas barrier performance, such as EVOH, PET,nylon, PBT, PA, POM, etc., for pressurized pens, and functions toprotectively connect the rear end part 10 of a metallic writing pointassembly 6 and the front end of an elongate ink tube 11. This joint 1,as shown in FIGS. 4 and 5, is formed basically in a cylindrical shapehaving an approximately nozzle-like form at the front end part 3. Thebore in this front end part is formed to be smaller in diameter thanthat of the other part of the front end part 3. A point assembly holder(also called plastic mouthpiece) 4 having an approximate cap-likesection is tightly fitted on the front end part 3. An annular flange 5is projected radially outwards from the outer peripheral surface at theapproximate center of joint 1. This flange 5 abuts the opening front endof inner barrel 20.

Writing point assembly 6 is formed of, for example, stainless steel, orthe like, which is excellent in erosion resistance, corrosionresistance, magnetism, IH heating performance, etc. As shown in FIGS. 4and 5, this writing point assembly 6 including a rotatable ball 8 at afront end part 7 is formed so that its mid part 9 is formed to bemarginally greater in diameter and its rear end part 10 is fitted intothe front end part 3 of joint 1 by electromagnetic induction heating,bonding or the like. Ink tube 11 is formed of translucent PP, PET resin,PE, recycled plastics or the like, for example, to be a hollow cylinderby extrusion molding. This ink tube 11 is filled up with ink (black,red, vermilion, blue or any color of ink) 12, and the front end part isinserted into joint 1 from its terminal end while the frontmost end isfitted and connected to the rear end part 10 of writing point assembly 6by press fitting, welding or any other method.

As shown in FIGS. 4 and 5, inner barrel 20 is formed in an elongatecylindrical form or in a cup-like form, specifically using apredetermined resin such as ABS, PP, PS, PE, recycled plastics, etc.,which is excellent in impact resistance, mechanical properties and thelike, or using a material also considering gas barrier performance, suchas EVOH, PET, nylon, PBT, PA, POM, etc., for pressurized pens. The innerbarrel is fitted to the rear end part of joint 1 with its open front endabutted against a flange 5 and hermetically encloses ink tube 11 leavinga space thereto. A pressurized gas 21 such as nitrogen, air or the likeis charged in this space, to constitute a pressurized writinginstrument. An annular positioning flange 22 is projected radiallyoutwards from the outer periphery in the front end part of inner barrel20. This positioning flange 22 abuts the open terminal end of holder 4and is either fitted or welded.

As shown in FIGS. 6 and 7, conductive ring 40 is formed of, for example,stainless steel which is excellent in erosion resistance, corrosionresistance, magnetism, plated iron or the like. Stainless steels SUS430,SUS304 etc., are preferably used.

Referring to an example of manufacturing a writing instrument of theabove configuration, first, conductive ring 40 is fitted and fixed tothe outer peripheral surface at the terminal end of joint 1, and joint 1and writing point assembly 6 are fitted together, forming an assembledwriting element. After preparation of the assembled writing element, ink12 is charged into ink tube 11 and the assembled writing element isinserted to the tube, completing an assembled tube.

Next, the assembled tube is press fitted into inner barrel 20 whilepressurized gas 21 is charged therein. Then as electromagnetic inductionheating is applied from exterior around conductive ring 40, conductivering 40 is heated so that joint 1, inner barrel 20 and conductive ring40 are joined by welding. When joint 1, inner barrel 20 and conductivering 40 have been welded, electromagnetic induction heating is stoppedfor cooling and solidification, whereby it is possible to obtain aperfect gas or ink 12 leakage-free structure.

Upon electromagnetic induction heating of conductive ring 40, heatingefficiency may and should be enhanced by minimizing the gap betweeninduction coil 31 and conductive ring 40 so that many magnetic fluxeswill concentrate on conductive ring 40. Since conductive ring 40 isgiven in an annular form, the generation efficiency of eddy current canbe particularly enhanced upon electromagnetic induction heating,producing preferable result. When conductive ring 40 is formed ofstainless steel (e.g., SUS430, SUS 304, etc.), various effects such asimprovement of the surface adhesion due to rust resistance; improvementof the generation efficiency of eddy current and excellent heatingefficiency due to high electric resistance can be obtained.

According to the above configuration, it is possible to fit and fixjoint 1 to inner barrel 20 reliably and tightly by electromagenticinduction heating even if, for example, part material that is prone tocrack when press fitted hence cannot be forcibly press fitted is used orif small scratches were formed during assembly. Therefore, there is nofear of pressurized gas 21 leaking, hence there is no fear of inkleakage and the like, which would occur as a result of gas leakage. Inaddition, since electromagnetic induction heating that is characterizedby rapid heating and non-contact heating (needing no electrode) is used,unlike the case of ultrasonic joining it is possible to markedlyeffectively solve the critical problems such as dislodging of ball 8supported by writing point assembly 6, blotting and flushing of ink 12and others. Further, unlike the case of ultrasonic joining, workstability as well as improvement of work speed can be expected.

Further, even in a case where a material that cracks with passage oftime when it is subjected to normal press fitting, such as PS, AS, PC,cyclic polyolefin, EVOH, or the like is used, it is possible to adhereit in a stress-free state by virtue of heating. Thus, since crackshardly occur, this permits easy material selection. In addition, sinceconductive ring 40 is not of a single plate-like form but of acontinuous form, welding will not become partly localized on theperipheral surfaces of joint 1 and inner barrel 20, but can be doneuniformly and appropriately on the peripheral surfaces of joint 1 andinner barrel 20. Further, according to the induction heating method,high-temperature heating and high-speed control can be expected so thatit is possible to improve productivity on the production line (quality,yield, operating rate, flexibility, space, maintenance operatingcontrol, etc.). As a result, it is possible to satisfy the demands forappearance, cost, productivity and performance.

In the above embodiment, joint 1 and inner barrel 20 are welded to eachother by electromagnetic induction heating of conductive ring 40.However, the present invention should not be limited to this. Forexample, writing point assembly 6 may be heated by electromagneticinduction so as to weld joint 1 and writing point assembly 6 at thepredetermined area (indicated by broken lines in FIGS. 4 and 5) 30, orwriting point assembly 6 and ink tube 11 may be welded. In this case,the whole of the writing point assembly may be heated by electromagneticinduction or only the predetermined area 30 of writing point assembly 6,specifically the rear end part 10 may be heated by electromagneticinduction so as to inhibit discoloration and other effects entailed withheating of unnecessary portion. Further, the invention is alsoapplicable to any joint between components similar to writinginstruments, such as a barrel and tail plug, a cap and a clip, a plasticmouthpiece and a barrel, and the like.

Industrial Applicability

As has been described, according to the present invention, since thewriting point assembly is welded to the holder and/or the ink tubewithout using ultrasonic waves, the writing point assembly will not beaffected by ultrasonic waves, hence dislodging of the ball supported atthe front end of the writing point assembly as well as degradation andflush of ink, defects such as splitting during writing and the like canbe effectively prevented. Further, it is possible to maintain theinitial strength of the fitted portion of the writing point assemblyeven if it is affected by external force, ambient temperatureinfluences, creep deformation of the material and the like. Thus,dislodging of the point assembly, cracking at the press fitted portionor ink leakage will not occur.

Further, in the present invention, if only the rear end part of thewriting point assembly is heated without heating the front end part, itis possible to effectively prevent waste of heating of unnecessaryportions, degradation due to heating of areas other the area to bewelded, adverse effects on writing due to thermal deformation of thewriting part and other harmful effects.

For the aforementioned heating, if the writing point assembly made ofmetal is induction heated at the predetermined area with an inductioncoil, it is possible to surely prevent the aforementioned harmfuleffects caused by ultrasonic heating.

It is also possible to achieve welding in the same manner with a simpleconfiguration if the rear end of the writing point assembly is heatedwith a heated trowel.

Further, if the heated portion of the writing point assembly is formedof stainless steel (SUS430 is especially preferable), it is possible toachieve reliable and precise bonding in a high efficiency withoutsuffering any degradation if induction heating is done.

In the case where the writing instrument is a pressurized ball-pointpen, it is possible to perfectly prevent gas leakage and hence providestable quality.

Further, even in use of a material that cracks when it is subjected tonormal press fitting or a material that presents less elongation, crackscan be effectively prevented by virtue of stress relieving owing toheating.

Moreover, the present invention is effective in firmly connecting theparts of a writing instrument, for example, a joint and an inner barrelto thereby inhibit leakage of fluids such as gas, ink, etc., as well asproviding a strong anti-dislodging configuration. Also, even if amaterial that is prone to crack due to press fitting is used, it ispossible to obtain a crack-free joining method because the parts can befixed with stresses removed.

1-17. (Canceled)
 18. A writing instrument comprising: a writing pointassembly having a writing part at the front end thereof; and an ink tubefor supplying the writing point assembly with ink stored therein,characterized in that the writing point assembly formed of metal isfitted into a surrounding holder or/and the ink tube with apredetermined area of the fitted portion brought into close contacttherewith and heated so that the resin around the predetermined area ofthe writing point assembly fuses or softens to weld the writing pointassembly to the holder or/and ink tube.
 19. The writing instrumentaccording to claim 18, wherein the heated portion of the writing pointassembly is formed of stainless steel.
 20. The writing instrumentaccording to claim 18, wherein a pressurized gas is sealed in theinterior forming a pressurized ball-point pen.
 21. The writinginstrument according to claim 18, wherein the holder is formed of aresin presenting a tensile elongation of 20% or less (based on ASTMD638)such as polycarbonate, ABS, cyclic polyolefin, modified polyphenyleneether, polystyrene or the like, and the holder and the writing pointassembly are welded.
 22. The writing instrument according to claim 18,wherein only the rear end part of the writing point assembly is heatedwithout heating the front end part of the writing point assembly. 23.The writing instrument according to claim 18, wherein the predeterminedarea of the writing point assembly made of metal is induction heatedwith an electromagnetic induction coil.
 24. The writing instrumentaccording to claim 18, wherein the rear end of the writing pointassembly is welded by heating with a heated trowel.
 25. The writinginstrument according to claim 22, wherein heating is effected byinduction heating using an electromagnetic coil.
 26. The writinginstrument according to claim 22, wherein the rear end part of thewriting point assembly is welded by heating with a heated trowel.
 27. Awriting instrument parts connecting structure for connecting parts of awriting instrument, characterized in that each part is formed of resin,and a conductor is arranged between the parts and brought into closecontact with the parts and welded by heating.
 28. A writing instrumentparts connecting structure for connecting parts of a writing instrument,characterized in that a joint and a cylindrical element are formed ofresin, a conductor is provided in close contact between the joint andthe cylindrical element, and the conductor, joint and cylindricalelement put in close contact are welded.
 29. The writing instrumentparts connecting structure according to claim 27, wherein the conductoris in the form of a stainless steel ring.
 30. The writing instrumentparts connecting structure according to claim 27, wherein the conductoris heated and welded using electromagnetic induction heating.
 31. Thewriting instrument parts connecting structure according to claim 28,wherein the joint is interposed between the point assembly and the inktube of the writing instrument so as to join these elements and thecylindrical element is made to serve as an inner barrel of the writinginstrument so as to cover the ink tube.
 32. A writing instrument partsconnecting method for connecting parts of a writing instrument,comprising the steps of: forming each part from resin; arranging aconductor between the parts; and heating the conductor byelectromagnetic induction after setting the parts into close contactwith the conductor, so as to weld the parts to the conductor.
 33. Awriting instrument parts connecting method for connecting a joint and acylindrical element, both made of resin, comprising the steps of:arranging an annular conductor between the joint and the cylindricalelement; and heating the conductor by electromagnetic induction aftersetting the conductor into close contact with the joint and cylindricalelement, so as to weld the joint and the cylindrical element.
 34. Thewriting instrument parts connecting method according to claim 32,wherein the conductor is given in the form of a stainless steel ring.